Overhead support beams used for building structures have long been made of wood as well as steel. Whereas steel beams are typically in the form of what are referred to as I-beams, having upper and lower flanges connected by a web and thus resembling the letter I, wood beams have historically been made in the form of rectangles, i.e., 4".times.6", 4".times.8", etc. A restriction on the use of rectangular wood beam supports is the size of a beam that can be produced from available tree sizes which over the years have become smaller and smaller.
A process of producing wood I-beams has been developed which does not rely on tree or log size. Flanges are produced by the process referred to as LVL or laminated veneer layers and the web between the flanges is produced by the process referred to as OSB or oriented strand board. The LVL process stacks sheets of veneer that are typically 4' wide and 8' long and, e.g., 0.1" thick. The ends of the sheets are scarfed and end spliced together (glued) to extend the length as desired. The spliced ends of overlying sheets are staggered to produce a consistent strength throughout the length and the elongated stacks are cut into strips, e.g., having a thickness of 11/2" to 31/2", a width of 4" and a length of 28' to 65'.
The OSB process involves first reducing a wood material to strands which are then oriented in a common direction to produce strand layers. Alternating overlying layers have the strands oriented 90.degree. from the underlying layers and the layers are added as desired to achieve the desired thickness. Again the boards produced from the strands are cut into strips to achieve the thickness, e.g., 3/8" and width, e.g., 71/2" as desired for the web of the I-beam. The webs are not continuous and, e.g., 4' or 8' lengths are end butted between the flanges to produce the desired lengths of the I-beams.
The challenge then is to assemble the web strips (webs) and flange strips (flanges) together as an I-beam. In a known process, the web segments are provided with tapered side edges of a precise configuration and the flanges are provided with mated grooves. Glue is applied to the tapered sides and/or grooves and as the components are conveyed along a path, the flanges are guided onto the tapered side edges at each side of the web and the assembly of the center web and side flanges is compressed between rollers to squeeze the tapered side edges of the web into the grooves of the flanges. The compression rollers insure that the overall dimension between the outside faces of the flanges conforms to an established dimension, i.e., the dimension intended with the side edges of the web properly seated in the grooves of the flanges.
The above process has at least three deficiencies to which the present invention is directed. As the flanges and web are brought together and compressed, any variation in the groove size, tapered side edges, glue deposited or even surface imperfections (within the groove or on the tapered edges) will cause one side of the web to be more resistive to being seated in the groove than the other side. The result may be that one side is inserted to a greater depth than the other which produces bowing or skewing of the beam and can even produce cracking of a flange.
The process is continuous, e.g., producing repeated 28' to 65' I-beams with the flanges following one after the other as they are guided into the assembly process. The LVL board lengths (from which the flange strips are generated) are typically not precisely the same lengths (e.g., there can be 1/4" variance in a 30' to 65' length), and accordingly as the flanges from one board follow another board, there can be a slight disparity between the lengths of the flanges from one side of the I-beam to the other. Whereas a slight disparity can be tolerated, a series of mismatches compounds the difference and produces an unacceptable disparity. This requires periodic resetting of the stream of flanges and on occasion generates a rejected I-beam which is too short for that run of I-beams and will have to be cut down to a shorter standardized length. This is a costly waste of production and undesirable.
The third deficiency is the required shut down for resetting of the machinery when a change to a different I-beam size is required. There are numerous machines involved and all or most require adjustment relative to the conveyor when the I-beam depth or flange size is varied. This shut down is extremely expensive and reducing the shut down time is highly desirable.